The Molecular Genetics Core serves this Program Project by providing genetic analysis of skin biopsy samples and cultured cell models of skin tumorigenesis. The Core is divided into three subdivisions, based upon the kin the molecular analysis to be employed: 1) DNA Microarray Technology focusing on advanced DNA microarray technology for the analysis of mutation and patterns of gene expression, 2) Single Strand Conformational Polymorphism (SSCP) Analysis focusing on detection of mutations by SSCP to detect mutations in the p53, H-ras, and p16 genes, and 3) In Situ Hybridization focusing on analysis of nuclear retinoic acid receptors RAR and RXR. The DNA Microarray Technology Section will design and fabricate standardized DNA probe microarrays: 1) A Skin Cancer Gene Expression Array, which analyzes human and mouse gene targets as describes in this Program Project, as well as approximately 100 additional gene targets important in tumor biology; 2) An array to analyze 48 mutational hot spots in p53, 3) An array to analyze the mutational hotspots in K-ras, and H- ras, simultaneously and 4) in order to accommodate the exploratory phase of several projects, the DNA Microarray Core will also collaborate in the fabrication of DNA microarrays in which the probe elements are cDNA amplicons, generated by PCR. The DNA Microarray ore will assist Project Researchers in hybridization and detection methodology, including a robotic workstation for microdispensing of hybridization and wash solutions. Detection and quantitation of hybridization signals will be performed in the Core in three ways: a confocal scanner, a proximal imager, and a cooled CCD camera. The SSCP Section will employ SSCP to establish the frequency of p53, p16, and H-rs mutations in subjects with AK, non-melanoma skin cancers, and controls. Special emphasis is placed on monitoring these endpoints as a marker of efficacy of chemopreventive agents and as the basis for development of new markers for dysplastic nevi and melanoma risk. The In Situ Hybridization Section will monitor the expression of RAR and RXR receptors, to test the hypothesis that their expression is suppressed in premalignant lesions and that pharmaceutical treatments can restore proper levels of expression in the skin.